The SEA Index is a collaborative effort which involves key industry players, from shipyards to operators and yacht owners.

With the launch of SEA Index Phase II, supported by the independent certification company Lloyd’s Register, the scope and accuracy of the tool is increased.

All those involved in the SEA Index development agreed to share data to help establish the benchmarks.

The SEA Index is considered a work in progress as more data is compiled and, aims to become a multi-faceted tool.

SEA Index Phase II provides an objective assessment, taking into account the typical operational profile of superyachts (at berth, anchor or cruising).

This pioneering carbon energy efficiency assessment tool includes innovative propulsion systems and alternative fuels.

SEA Index Phase II can rate hybrid and battery-based propulsion systems and innovative auxiliary power features can also be accounted for.

The SEA Index uses benchmark data to assess how superyachts entering the calculation process perform against the rest of the average fleet.

Most existing measurements only cover commercial ships, which gave the SEA Index the opportunity to fill the gap in the superyacht industry.

Existing measurements today


– MARPOL resolutions and annexes (Annex VI – Prevention of Air Pollution from Ships)
– Energy efficiency measures: EEDI, SEEMP, EEOI

Classification societies

– Green notations as proof of voluntary compliance with additional measures, including all life cycle steps, from design to recycling

Independent labeling systems

– Environmental Shipping Index evaluates performance in reducing air emissions
– Clean Shipping Index includes air pollution as well as chemicals, water and waste
– Blauer Engel for environmentally friendly ship design

How does the SEA Index work? 

The SEA Index is the result of a technical formula which calculates an environmental ratio from data across a range of criteria.

Set against benchmarks and the average ratios of the superyacht fleet, the SEA Index assessment reveals if any given superyacht stands above or below the new baseline. If the relative environmental performance is truly excellent, it is awarded five stars, the highest rating. The number of stars decreases for yachts with a lower relative efficiency performance. Superyachts can then carry the SEA flag and be recognised for their environmental performance.

An evolutive method 

While impact is measured through CO2 emission levels, it is not the only criteria. One of the important aspects is that the index takes into account the CO2 per gross ton, which is representative of the volume of the vessel’s enclosed space – a measure of the utility of the vessel without influence of the space usage.

The online calculator gives applicants an initial rating of the yacht’s CO2 polluting emissions.  Upon review of adequate data documentation, the next step, is for each yacht applicant  to apply to become a member of the Superyacht Eco Association and be remitted with their exclusive SEA Index certificate. This certificate is independantly verified by Lloyd’s Register, the internationally-renowned independant certification company.


The rating metric of the SEA Index is based on the approach taken by the UN’s International Maritime Organisation, plus specific customisations for application to superyachts. The initial benchmarks were generated from data provided by 130 yachts, ranging from 40-140 meters in size, with every data point of the assessment collected and validated by the SEA. Phase II of the SEA Index has included data from over 300 yachts. The approach taken is to calculate a representative CO2 emission rate at sea and a representative CO2 emission rate when at anchor/berth and weight them by a nominal operating profile